Determination of Equivalent Thermal Conductivity of Window Spacers in Consideration of Condensation Prevention and Energy Saving Performance

Abstract

This study investigated the impact of thermally improved spacers (TISs) on the condensation prevention and energy saving performances of residential windows. The temperature factor and total U-value were analyzed with the two-box model, by which the TISs are represented with the equivalent thermal conductivity. The results showed that the TISs could increase the temperature factor by up to 12%, and this significantly improved the condensation prevention performance. In addition, it was proved that the TIS enables the prevention of the condensation at an outdoor temperature that is 4.2 • C to 15.7 • C lower compared with the conventional spacer. Also, it was shown that the TISs reduce the total U-value by an amount from 0.07 W/m 2 K to 0.12 W/m 2 K, implying that the heat loss through the window is reduced by a rate from 2.8% to 8.2%. In addition, the results of the whole building energy simulation proved that the TISs can reduce the annual heating-energy consumption by a rate from 3.0% to 6.3%. The results were then used for the development of monographs to determine the equivalent thermal conductivity of a window spacer that can meet the performance criteria in terms of condensation prevention and energy saving.

Effect of Surface Thermal Resistance on the Simulation Accuracy of the Condensation Risk Assessment for a High-Performance Window

“…Insulating spacers have been introduced to reduce heat loss caused by the thermal bridge in the edge-of-glazing. Previous research has shown that improving spacers could significantly reduce the energy lost through multi-pane windows [11][12][13]. In high-performance windows, such as triple-glazed windows, insulating spacers can reduce window U-value by 12% compared to the U-value with aluminum spacers [11].…”

“…Shin et al [12] showed that a two-box model could be useful for the two-dimensional thermal simulations to investigate the impact of the spacers on the window thermal performance. Arasteh et al [15] used five different laboratories and six different simulators to evaluate the thermal transmittance (U w ) of 16 windows.…”

A New Metre for Cheap, Quick, Reliable and Simple Thermal Transmittance (U-Value) Measurements in Buildings

“…They provide the retrofitting measures for the variables of interest both before (to assess the retrofitting to be carried out) and after (to evaluate the retrofitting results and obtain the reliability of improvement). In general, measurements of temperature [ 6 , 7 , 8 , 9 ] and relative moisture [ 10 , 11 ] both indoor and outdoor, solar radiation [ 12 , 13 ], envelope thermal transmittance ( U-Value ) [ 14 , 15 ], power consumption by electrical circuits [ 16 ], etc., are required.…”

The Feasibility of Improving the Accuracy of In Situ Measurements in the Air-Surface Temperature Ratio Method

“…The average method is one of those most commonly used to evaluate the thermal properties of building elements using in situ measurements [9]. The U-value is measured under quasi-steady state conditions [10][11][12][13][14][15]. However, the latter are difficult to measure and thus the average heat flow of the building envelope must be measured for a sufficiently long time.…”

“…However, this method takes 7 to 14 days for heavy structures and data collection takes at least 3 days. Previous studies [10][11][12][13][14][15] using the HFM method measured the U-value of the building envelope over a long period of seven days or longer. In other words, it does not provide a means to measure the thermal performance of a building over a short period of time.…”